CHELYABINSK, Russia — A small army of workers set to work Saturday to replace the estimated 50 square acres of windows shattered by the shock wave from a meteor that exploded over Russia’s Chelyabinsk region.

The astonishing Friday morning event blew out windows in more than 4,000 buildings in the region, mostly in the capital city of the same name and injured 1,200 people, largely with cuts from the flying glass.

Forty of the injured remained hospitalized on Saturday, two of them in serious condition.

Regional governor Mikhail Yurevich on Saturday said that damage from the high-altitude explosion — estimated to have been as powerful as 20 Hiroshima bombs — is estimated at $33 million. He promised to have all the broken windows replaced within a week.

But that is a long wait in a frigid region. The midday temperature in Chelyabinsk was minus-10 F, and for many the immediate task was to put up plastic sheeting and boards on shattered residential windows.

More than 24,000 people, including volunteers, have mobilized to cover windows, gather warm clothes and food and make other relief efforts.