TRENTON, N.J. - Officials are closely watching an ice jam on the Delaware River that poses a flood threat to portions of New Jersey and Pennsylvania.

The river clogged with ice in Trenton during record-breaking cold temperatures earlier this week. There's concern what will happen downstream when the ice starts to melt.

The New Jersey Statehouse garage, some southbound lanes on Route 29 in Trenton and Route 32 north in Yardley, Pa., are closed because of flooding.

The National Weather Service has issued a flood watch for Mercer and northwestern Burlington counties in New Jersey and lower Bucks County and Philadelphia in Pennsylvania through Thursday evening.

Forecasters say the river is at 19.3 feet and fluctuating below the flood stage of 20 feet. The river is expected to fluctuate throughout the day.