US Congressional investigators are seeking more information about advanced brake technology used as a remedy for unintended acceleration in Toyota vehicles.

The House of Representatives Energy and Commerce Committee has asked for additional documents on brake override features that may already be equipped on some existing vehicles and wired to the electronic throttle system.

Toyota has previously told Congress publicly that brake override technology may not be applicable to all older vehicles because of incompatible designs in vehicle systems.

However the committee said it has been told by outside technical experts that some older model Toyotas may have an override system that activates when the throttle system registers a software glitch.

“Neither you nor Toyota’s electronics experts informed the committee that some older model vehicles may already have a brake override function” tied to accelerator software, the committee said in a letter to the carmaker.

Toyota said it was reviewing the letter.

Toyota has pledged to install software on cars and trucks, beginning with the 2011 model year, that allow braking systems to override acceleration to ensure the driver can stop a vehicle in all circumstances.

Brake override is considered by lawmakers and National Highway Traffic Safety Administration (NHTSA) regulators to be an important response to the question of unintended acceleration which was behind massive Toyota recalls in 2009 and this year.