A man has climbed on top of a lorry close to Cuadrilla's controversial fracking site in Preston New Road, Little Plumpton, police said.
A spokesman said the road is down to one lane, with officers called out at around 10.20am today.
The site has been a constant target for anti-fracking demonstrators.
Police have asked drivers to avoid the area if they can, or to allow extra time for their journeys if they can't.
More to follow