WASHINGTON, April 11 (Reuters) - The National Highway Traffic Safety Administration (NHTSA) said Thursday it is investigating a March 3 fatal crash between a Ford Mustang Mach-E and two stationary cars in Philadelphia in which an advanced driver assistance system could have been in use.

This is the second recent Ford crash under investigation by the auto safety regulator and the National Transportation Safety Board (NTSB) in which a driver assistance system is suspected of being in use.

The March 3 crash involved the Ford striking two stationary vehicles on the I-95 interstate highway in Philadelphia killed two people and shut down traffic for hours. The NTSB said it is investigating in coordination with the Pennsylvania State Police, which declined to comment.

Ford offers BlueCruise, an advanced hands-free driving system that operates on 97% of U.S. and Canadian highways with no intersections or traffic signals.

In March, NHTSA and the NTSB said they were investigating the use of an advanced driver assistance system in a Ford Mustang Mach-E that was involved in a Feb. 24 fatal crash in San Antonio, Texas in which the Mach-E struck rear of a Honda CR-V that was stationary in a traffic lane on Interstate Highway 10. A San Antonio police report said the Ford had "partial automation" engaged at the time of the crash.

Ford said it was recently made aware of this incident by the NTSB and informed NHTSA, which requires automakers to report all fatal crashes involving advanced driver assistance systems.

"We are researching the events of March 3 and collaborating fully with both agencies to understand the facts," Ford said.

NHTSA has opened special crash investigations into the two recent Ford crashes. The agency typically opens more than 100 special crash investigations annually into emerging technologies and other potential auto safety issues.

Since 2016, NHTSA has opened more 40 Tesla special crash investigations in cases where driver systems such as Autopilot were suspected of being used, with 23 crash deaths reported to date. Tesla in

December agreed to recall 2 million

vehicles to install new safeguards for Autopilot.

The NTSB has opened several investigations in recent years into advanced driver assistance systems including Tesla's Autopilot. (Reporting by David Shepardson; Editing by Chizu Nomiyama and Nick Zieminski)