NEW YORK - (AP) - Mayor Michael Bloomberg gave a press conference tonight, saying it could be the weekend before the lights come on for hundreds of thousands of people plunged into darkness by what was once Hurricane Sandy.

Bloomberg said it could also be four or five days before the subway, which suffered the worst damage in its 108-year history, is running again. All 10 of the tunnels that carry New Yorkers under the East River were flooded.

Sandy killed 18 people in New York City, the mayor said. The dead included two who drowned in a home and one who was in bed when a tree fell on an apartment. A 23-year-old woman died after stepping into a puddle near a live electrical wire.

"This was a devastating storm, maybe the worst that we have ever experienced," Bloomberg said.

Some bridges into the city reopened at midday, but the Brooklyn-Battery Tunnel, connecting Brooklyn to Manhattan, and the Holland Tunnel, between New York and New Jersey, remained closed. And service on the three commuter railroads that run between the city and its suburbs was still suspended.

Gov. Andrew Cuomo said bus service would be restored at 5 p.m. EDT, on a limited schedule but free. He said he hoped there would be full service on Wednesday, also free.

The New York Stock Exchange was closed for a second day, the first time that has happened because of weather since the 19th century, but said it would reopen on Wednesday.

Con Edison said it would be four days before the last of the 337,000 customers in Manhattan and Brooklyn who lost power have electricity again.

For the Bronx, Queens, Staten Island and Westchester County, with 442,000 outages, it could take a week, Con Ed said. Floodwater led to explosions that disabled a power substation on Monday night, contributing to the outages.

Click 'play' to watch the news conference.