A firework thrown or launched from the back of a boat on Lake Tulloch ignited a fire that broke out Monday and continued smoldering Tuesday on steep ground above the manmade reservoir, just upstream from the O’Byrnes Ferry Road bridge.

Chief Josh White of Cal Fire’s Tuolumne-Calaveras Unit disclosed the cause of the fire Tuesday.

The Tulloch Fire was reported to dispatchers shortly after 3 p.m. on Memorial Day by Tuolumne County Sheriff’s deputy Sam Egbert, who was patrolling the reservoir for holiday enforcement.

Daytime highs for Sonora and Jamestown reached 90 degrees and hotter on Monday, and the blaze prompted response of pilots in retardant-dropping planes and water-dropping helicopters, scores of firefighters on the ground, and at least one investigator.

As of Tuesday afternoon, the burn area was said to be 80 percent contained, and it was estimated to be 82 acres. There were about 70 fire personnel assigned to the burn Tuesday, including five engine crews and three inmate crews, according to Lindy Shoff of Cal Fire.

No estimate for costs of fighting the fire was available. Cal Fire’s investigation of the blaze’s cause was continuing. No citations, charges or arrests were announced in connection with the cause of the fire.

White disclosed the cause of the fire one day after it broke out in part to respond to a Copperopolis lawyer who wrote emails to White and Cal Fire Director Ken Pimlott on Tuesday.

Thomas Meyer asked White to ban all burning by 8 a.m. June 1.

“As a resident of Copperopolis and a member of the Calaveras Bar Association, I find that your allowing of burning while you complain about ‘escaping debris’ causing fires sheer insanity,” Meyer wrote.

Meyer emailed Pimlott later Tuesday.

“Right now there is a 100 acre fire — Tulloch Fire — still burning 8 miles from Copperopolis where I reside. The weather is hot, dry and there is a 10 plus mile an hour wind everyday, yet Mr. White refuses to ban burning,” Meyer wrote.

The safety of Calaveras and Tuolumne counties is at high risk, Meyer wrote, saying his family along with thousands of families are at risk.

“We are still cleaning up from the Butte Fire,” Meyer wrote. “We don’t need another one, this time caused by Cal Fire’s failure to ban burning. Please stop this insanity and ban burning in Calaveras and Tuolumne counties.”

White said he was attending a meeting out of town and shared his full response to Meyer.

Since May 1, when burn permits were required, there have been five pile burns in Tuolumne and Calaveras counties that have escaped the person’s control and required fire department responses, White said in his email to Meyer.

“In each of these instances, the person did not have a burn permit and was not following any of the permit rules that require adequate clearance, the presence of water and tools, and a person remain in attendance at all times,” White said. “Three of these were issued a citation and the other two cases have been referred to the District Attorney’s Office for prosecution.”

Several fires occurred Monday, White said. There were about three fires on Flood Road believed to be sparked by a boat trailer chain dragging and producing sparks.

“We also had the Tulloch Fire that started from a firework off the back of a boat, just upriver from the O’Byrnes Ferry bridge,” White said.

As far as burn permits and burn restrictions, White said Cal Fire evaluates weather and fuel conditions on a daily basis.

“My plan is to restrict burning to the night time hours of 7 p.m. to 8 a.m. beginning tonight,” White said in his email to Meyer on Tuesday. “This time frame is when the air cools down and the humidity rises, reducing the possibility of a burn pile escape. This is consistent with our burn permit management during this time of year.”

White pointed out Cal Fire issues hundreds of burn permits each spring and, as of Tuesday, the Tuolumne-Calaveras Unit had not had a single burn pile escape the control of a permit holder.

“Homeowners at higher elevations are currently dealing with tree mortality of epidemic proportions,” White said. “It is important for these homeowners to have the ability to remove fuels from around their structures and safely dispose of them. It is my intention to allow people to continue safely doing this and not restrict that ability due to a handful of negligent people.”

In a phone interview Tuesday, Meyer said, “Night permit burning is crazy, too.”

In a follow up email, Meyer wrote to White and Pimlott, “Let me get this straight, you will continue to allow burning 7pm to 8am so that the permitted people can burn along with the thousands of unpermitted people to burn.

“It boggles the mind that you would think burning at 7 pm still daylight and hot and windy will help the situation. It is also craziness to allow people to burn dead trees in a 4X4 contained area. They can be hauled off! You are putting lives at risk! A fire not set is safer than any dead tree.”

Later Tuesday afternoon, Cal Fire Tuolumne-Calaveras Unit personnel distributed an announcement of White’s decision to restrict pile-burning to night hours only.

This week’s weather is being billed as a Mother Lode heat wave. Daytime highs in the 90s may approach triple digits by Saturday. Overnight lows are expected to remain in the 60s.