Authorities in San Francisco said several downtown streets were closed when a box carrying 6 tons of steel wound up dangling from a disabled crane.

Police said the streets were blocked Sunday afternoon when the crane atop the former Bank of America building malfunctioned and threatened to send the steel plummeting 600 feet to the ground, the San Francisco Chronicle reported Monday.

The box had to be lowered via hand crank, a process estimated to take up to 6 hours.

The streets were reopened about 7 p.m. Sunday.