Image copyright AP Image caption Wildlife experts tried for hours to coax the seal back into the water

A half-ton elephant seal that had tried to cross a road in Northern California has been tranquilised by rescue officials.

It followed a day-long stand-off in which wildlife experts used horns and paddles to try to encourage the animal back into the water.

The seal tried several times to cross the road before a vet tranquilised her using a pole-mounted syringe.

The sedated seal was to be released back into the wild at a nearby colony.

Teams from the Marine Mammal Center and the San Pablo Bay National Marine Sanctuary were called in on Monday following reports that the seal was disrupting traffic on Highway 37 in Sonoma County.

Attempts were made to frighten the animal back into the water using horns and paddles, but the seal refused to budge.

"She's a 900-pound elephant seal. She pretty much does what she wants," Barbie Halaska, a research assistant at the mammal centre, was quoted by the San Francisco Chronicle as saying.

After the seal was sedated, an ultrasound revealed that she was pregnant.

The seal was driven to the Point Reyes National Seashore to recover before being released at Chimney Rock.