Parts of Massachusetts, including Boston, were under flash flood warnings on Friday morning, the National Weather Service said, as thunderstorms swept across the eastern portion of the state.

The Weather Service in Providence, R.I., said that a thunderstorm was possible until 1 p.m., and that some of the storms could bring heavy rain.

Just after sunrise on Friday, a line of thunderstorms strengthened over parts of New England and probably caused tornadoes. A tornado warning was in effect for parts of Massachusetts until 10:45 a.m., the Weather Service said.

The flash flood warnings were in effect until 11:45 a.m. Flash flooding was most likely to occur near highways and small creeks and streams, and in urban and low-lying areas, the Weather Service said.

Judson Jones contributed reporting.