SYLMAR, LOS ANGELES (KABC) — One person was detained Thursday night after shots were fired on the 210 Freeway in the Pasadena area, authorities said.

It happened around 9 p.m. Thursday.

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According to the California Highway Patrol, the shooting was reported on the westbound lanes of the 210 Freeway at Allen Avenue.

It’s unclear what sparked the shooting but CHP said at least one of the people involved was a semi-truck driver. The truck was stopped just before the 14 Freeway.

Authorities said the person who reported the shooting was an off-duty officer, though the agency he or she is a part of was not immediately disclosed. It’s also unclear if the officer was a victim in this incident, but CHP said no injuries were reported.

This is a developing story. This article will continue to be updated as more information becomes available.