A bicyclist was seriously injured when he was hit by a truck in North Lindenhurst, closing eastbound Route 109 for several hours during Friday’s morning commute, Suffolk County police said.

Richard Roth, 60, was crossing Route 109 when a U.S. Postal Service truck traveling south on Straight Path was attempting to make a left turn onto Route 109 at about 6 a.m. The truck struck Roth, of West Babylon, seriously injuring him, police said.

A department spokeswoman said Roth was taken to Good Samaritan Hospital Medical Center in West Islip with serious injuries.

The truck’s driver, Thomas Borrelli, 56, of Ridge, was uninjured.

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Police impounded the truck for a safety check, and First Squad officers are still investigating. Those with information should call 631-854-8152.

With Laura Blasey