HOUSTON — A lawyer for state troopers says an infrared security system designed to detect intruders wasn't working the night that an arsonist torched the governor's mansion.

The security system used infrared beams that would sound an alarm to troopers in a carriage house behind the mansion if someone got over the property walls.

Don Dickson, an Austin lawyer who represents the Texas State Troopers Association, told the Houston Chronicle that one of his clients notified Department of Public Safety superiors that the system wasn't working.

DPS spokeswoman Tela Mange declined to comment, saying that the fire is still under investigation.

The DPS cut back its security at the 152-year-old mansion last year after Gov. Rick Perry and his wife moved out at the start of a $10 million renovation job. Only one trooper was on duty when the fire broke out early on the morning of June 8.

State officials said this week that security cameras captured video of someone lighting an object and throwing it on the front porch. The fire caused extensive damage, although Perry said the mansion can be salvaged.

The Chronicle reported in Saturday editions that the infrared system hadn't been working for at least four weeks despite complaints by troopers.

DPS authorized the return of the system to the manufacturer for repairs, said Edward Johnson, executive director of the Texas Facilities Commission, which is overseeing the mansion renovation but has no control over security.

"If it were me that was in charge of security and I had my (alarm) system in the shop, I would have substituted that with armed guards at the gates or at all the corners," Johnson said.

Dickson, the lawyers for the troopers group, said the officers frequently deal with broken-down gear.

"Equipment failures are not uncommon at the DPS," he said. "We have troopers all over Texas who have been notifying their supervisors that their cameras don't work or this doesn't work or that doesn't work. And it's hell getting them replaced."