A mudslide has blocked traffic on Maple Valley Highway approaching Interstate 405 and Renton.

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Another mudslide has blocked a busy traffic route Thursday morning, this time Maple Valley Highway approaching downtown Renton and Interstate 405.

Police tweeted just after 9 a.m. that all westbound lanes are closed, and only one eastbound lane is open for a few blocks beyond I-405.

The slide is near Carco Theatre and Classics sports bar, not far from the Cedar River. Public-works crews arrived to start clearing the area, but no reopening time has been estimated.

The highway is a major regional route serving outlying parts of Renton, northern Kent and the fast-growing Maple Valley commute corridor.

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This slide follows an earlier slide on Interstate 90 just east of Issaquah that has forced westbound traffic to detour through two-lane residential arterials.

Geotechnical inspectors are at the I-90 slide to determine whether more are likely to occur, said spokesman Travis Phelps of the Washington State Department of Transportation.

WSDOT thinks the slide at 5 a.m. was a relatively shallow “debris flow,” which Phelps compared to the frosting falling off a cupcake.

The top layer of soil became supersaturated from rain along with flowing water atop a slope, he said. It’s not a known slide area where an entire hillside has broken apart, he said.

There are no plans for a temporary slide barrier, he said.

One lane westbound is moving at I-90, while the two right lanes remain blocked.

Highland Park Way Southwest in Delridge will remain closed Thursday, says the Seattle Department of Transportation.