New York City has released 900 people from its jails in an effort to curb the spread of coronavirus among inmates.

Mayor Bill de Blasio’s announcement Tuesday afternoon came amid growing numbers of confirmed COVID-19 cases in guards and detainees at Rikers Island, the city’s most notorious jail, with a reputation for abuse and neglect of inmates.

On Monday evening, Rikers Island’s top doctor, Ross MacDonald, took to Twitter to share a grim outlook for the situation at the jail, calling it a “public health disaster unfolding before our eyes.”

More than 167 inmates and 137 corrections staff from Rikers have tested positive for the disease, up from 80 cases total just five days ago. Analysis by one legal aid group found that the rate of infection at Rikers was seven times higher than that in New York City, which is currently the epicenter for coronavirus in the U.S. For weeks, legal aid and civil rights groups have been urging the city to move quickly to remove vulnerable inmates from jails before the virus made its way inside.

The number of detainees released from city jails so far (900) is more than double than the number of people de Blasio said he was expecting to release last Friday (375). The people who were considered for release included those who are elderly or had underlying health risks making them particularly vulnerable to coronavirus, or those who’d been charged with nonviolent offenses or parole violations.

As of Sunday night, there were 4,640 people detained in New York City jails, according to Legal Aid.