BANGOR, Maine — The president of the New Hampshire gas company that installed a new heating system that apparently caused carbon monoxide poisonings at a Brewer apartment complex in August pleaded guilty Friday to unlicensed practice, his attorney said.

Concord Gas Heating Service President James Kane originally had his Bangor attorney Jay McCloskey enter a plea of not guilty in 3rd District Court on Thursday, but on Friday afternoon decided to change the plea for the misdemeanor charge to guilty.

“There was an agreement to pay a fine near the maximum of $1,000,” McCloskey said Saturday.

Kane was fined $970 for installing the furnace without a license.

“He had an expired license and had applied for a new license, but because the rates had changed, they sent back the paperwork,” McCloskey said. “He had to send a check. He got his license six or seven days after this [the installation] occurred.”

Kane and a technician of his company installed the new heating system at the River House, a 31-unit apartment complex on Penobscot Street.

The carbon monoxide poisoning at the River House, apparently caused by a separated furnace vent pipe, sent at least eight people to the hospital. Three of those needed treatment at St. Joseph Hospital’s hyperbaric chambers, and one was treated for nearly a week.

Employees who work for out-of-state companies are required to be licensed in Maine to work here.

Concord Gas did not have the required city permit to do the work, which would have required city staff to inspect the furnace, said Brewer Code Enforcement Officer Dave Russell.

At least four of the victims have hired a Bangor attorney, who last week filed notices indicating they plan to sue for damages to cover medical costs.