NEW YORK (CBSNewYork) – The MTA confirmed a software problem led to the subway system failure that shut down trains Friday night.

Andy Byford, president of the New York City Transit Authority, talked about the issue at a board meeting Monday morning.

The MTA is now checking the system to identify other potential problems.

Many subway riders were stranded on platforms in the sweltering heat Friday night. Others were stuck on trains.

The MTA says 27 trains were affected when the automatic train supervision system lost track of their locations.

“The ATS had gone down for the A division. That meant that lines 1-6 and the Times Square Shuttle. Once again, the RCC could not see where those trains were and did not know what their identities were,” Byford said.

The agency said it had to reboot the system that went down and restored service in about 90 minutes.