Garbage that fell from a refuse train onto the subway tracks at 14th Street caused a southbound Q train to get stuck twice Wednesday, resulting in delays on nine subway lines during the morning commute, the MTA said.

The garbage was on the tracks because of an “operator error,” an MTA spokesman said in a statement.

“Operator error caused garbage to not be properly secured on a southbound refuse train at 14th Street, causing garbage to fall on the tracks and impact following southbound service,” the statement said.

The Q train first got stuck at Canal Street shortly after 6 a.m. and then stalled again at the DeKalb Avenue station at about 6:45 a.m.

As a result, there were delays or service changes in place on the B, D, E, F, M, N, Q, R and W trains. Full service was restored on all lines throughout the day, but lingering delays and changes persisted until just before 5 p.m., according to the MTA.

The agency promised to discipline the worker who made the error.

"New York City Transit and the MTA have zero tolerance for worker errors that cause service problems," the agency said. "Appropriate disciplinary action will be taken as necessary pending the conclusion of the ongoing investigation."

Service on 7 trains was also impacted Wednesday morning due to a separate issue. A smoke condition in the Steinway Tunnel forced the MTA to suspend service between Queensboro Plaza and 34th Street-Hudson Yards for about a half-hour. Service in both directions resumed with delays by 9:30 a.m., the agency said.

Wednesday's train delays were just the latest in a long list of issues that have caused service disruptions this year, including a derailment and a track fire in July.