Humberside Police have closed a number of roads in Hull and Hedon this morning.
The force has taken the unusual measure as its responds to a series of aggravated vehicle thefts.
In a statement, it said: "We are currently responding to a number of aggravated vehicle thefts in the Hull and Hedon this morning.
"This has led to a number of road closures and numerous police resources being deployed.
"Enquiries are ongoing and if anyone has information that may be linked they are urged to call 101."
A full list of road closures has not been issued, but it appears to include Johnsons Corner in Hedon.
EYMS said its buses were diverting via Haven Basin Road and Sheriffs Highway due to a police incident.