Authorities have closed an almost mile-long stretch of West River Parkway after a small sinkhole formed next to the bicycle path near Mill Ruins Park on Wednesday morning.

The emergency road closure is between Portland Avenue and 4th Avenue N., and detours are posted for cars. Bike traffic has been diverted to the nearby pedestrian path for safety.

A passerby reported the sinkhole to the Minneapolis Park Board’s customer service line sometime after 8 a.m., said spokeswoman Robin Smothers. Workers assessing the damage measured the sinkhole at about 6 feet across and 15 feet deep, she said. The hole widens underground and appears to extend underneath the bike path.

Park board engineers immediately closed the surrounding area and intend to fill in the hole once city staff determine the parkway is safe. Rain may delay that process, Smothers said.

The parkway will remain closed until further notice.