Britain's government urged local officials across the country Sunday to urgently submit samples of tower block cladding after tests found that all samples tested so far have failed fire safety standards.

In London, officials tried Sunday to complete the evacuation of hundreds of apartments in four towers deemed unsafe, but faced resistance as several families refused to budge.

The government has collected 34 samples of external cladding — panels widely used to insulate buildings and improve their appearance — and all failed a "combustibility test," Community Secretary Sajid Javid said. The national testing was ordered after a June 14 fire engulfed Grenfell Tower in London, killing at least 79 people. The tower's cladding was believed to have rapidly spread that blaze.

The samples came from 17 different locations around the country, including London, Manchester, Plymouth and Portsmouth.

A public inquiry is due to determine how the unsafe cladding was allowed to be fitted onto Grenfell in the first place.

In north London, Camden Council ordered residents at Chalcots Estate to leave some 600 apartments late Friday as a precaution after fire inspectors found problems with the blocks' fire doors and gas pipes. The council said those issues, combined with the flammable cladding that encased the buildings, meant residents had to leave immediately.

Now hundreds of residents face up to four weeks in temporary accommodations as workers try to upgrade the buildings' fire safety features. Around 20 families wanted to stay put, but council leader Georgia Gould say they must leave.

Refurbishment of the Chalcots towers was overseen by Rydon, the same company involved in the recent renovation of the now-devastated Grenfell Tower.

London Mayor Sadiq Khan backed Camden Council's decision to evacuate the apartment blocks.

"I think they've done the right thing. Look, you've got to err on the side of caution. You can't play Russian roulette with people's safety," he told Sky News.