By Mike Dunn

PHILADELPHIA (CBS) — The City of Philadelphia has fully activated its emergency operations center, and three shelters are now open for city residents who have left their homes in advance of potential flooding from Hurricane Sandy.

About twenty different departments and agencies are involved in the monitoring of and response to the storm.

This morning, Mayor Nutter was making the rounds of the shelters and the neighborhoods of Philadelphia where the threat of flooding is greatest.

“We’ve really been pushing very, very hard the message, and helping people to understand, this is a serious storm — you need to take it seriously,” he told KYW Newsradio.

The 311 non-emergency call center remains open (see related story), and police commissioner Charles Ramsey is urging residents to save 911 for only the most dangerous issues that result from Sandy.

Previously, the mayor ordered the shutdown of all non-essential services of city goverment during the storm emergency (see related story).