Waste Management halted service Wednesday when Teamsters officially went on strike over wage and benefit concerns.

The region’s largest refuse service company serves about 220,000 customers in King and South Snohomish counties.

Teamsters Local 117, which represents 153 recycling-route drivers, joined Local 174, which represents the garbage-truck drivers, in the strike.

Teamsters 117, Waste Management and a federal mediator will continue to negotiate a new deal Saturday, according to sources.

“We are prepared to do this, provided the union leadership discontinues the pickets and allows our drivers to return to work,” Waste Management said in a statement released Friday. “Unfortunately, the union leadership refuses to allow our drivers to return to work and refuses to ensure uninterrupted service next week.”

Waste Management urges customers to go to its website, www.wmnorthwest.com, to check specific information regarding their communities.

Customers can direct questions to its website or customer service center at 1-800-592-9995.