Someone intentionally activated the emergency brakes on multiple New York subway trains on Tuesday, bringing them to a halt and disrupting “thousands of commutes,” the authorities said.

The Metropolitan Transportation Authority said the disruptions mainly affected the 2 and the 3 lines.

“If you see any suspicious behavior, please @ or DM us details ASAP, including car #, so we can get trains back on schedule,” the M.T.A. said in a tweet.

By 9 p.m. Tuesday, the trains were no longer delayed because of the emergency stops, the M.T.A. said.