A suspected chemical incident has seen police cordon off a business park and search two properties.
Officers and firefighters rushed to the scene on Chasewood Park Business Centre in Cannock, Staffordshire, with searches conducted, including at a business premises.
It is understood patrol cars remain at the site - with initial calls made in the early afternoon.
Customers at a nearby cafe and other businesses were evacuated in "manic" fashion, according to witnesses.
It is not yet known if anyone has been injured.
Residents have said they saw "loads of police cars" at about 3pm today in Heath Hayes.
Some said businesses have had to close, reports BirminghamLive.
A spokeswoman for Staffordshire Police said: "We are currently at the scene of a suspected chemical incident at a business premises in Heath Hayes, Cannock.
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"A cordon is in place around the Chasewood Park Business Centre on Hednesford Road as a precaution.
"We are also carrying out searches at a property on View Street, Hednesford, and at business premises on Wolverhampton Road, Cannock.
"Officers and colleagues from Staffordshire Fire and Rescue Service are at the scene."
West Midlands Ambulance Service has been approached to comment.
