SAN MATEO (CBS SF) — Authorities issued a severe traffic alert on U.S. Highway 101 due to police activity Tuesday afternoon that shut down lanes in both directions for over an hour.

The incident was initially reported and a Sig Alert issued at 1:14 p.m. of lane closures due to police department activity on 101 south of the San Mateo-Hayward Bridge.

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The 511.org Twitter account first posted about the incident at around 1:20 p.m., stating that all northbound lanes of 101 were closed in San Mateo south of state route 92. Additionally the left and center lanes of southbound 101 were blocked.

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Authorities were able to reopen the left northbound lanes a short time later, but the activity continued to close lanes in both directions over an hour later. Authorities have not provided any details on the nature of the police activity.

Shortly after 2:30 p.m., authorities said that the northbound right and center lanes remained blocked, but all southbound lanes had reopened.

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Moments later, authorities updated the situation, saying that all lanes had reopened as of 2:43 p.m. Drivers are advised to expect residual delays.