An earthquake of preliminary magnitude 3.9 struck early Wednesday outside of Montreal, Canada, according to the U.S. Geological Survey (USGS).

The temblor's epicenter was about 21 miles (35 km) northeast of Montreal and 6 miles (9 km) north-northwest of Beloeil, Quebec. It originated 6.2 miles (9.9 km) deep and struck at 12:19 a.m. local time (04:19 UTC), the USGS reports.

Earthquakes of this size tend to be felt by people in the area but typically do not cause significant damage, other than possibly broken windows and falling dishes or the toppling of unstable objects.

News reports indicated that the tremor caused no known damage, but it did confuse some residents. Authorities in the city of Laval, just north of Montreal, received more than 1,000 911 calls within 20 minutes of the quake, the CBC reported, and residents in Montreal flooded the phone lines as well.

"People were asking what exactly was happening," Montreal police Constable Simon Delorme told the broadcaster. "The 911 operators worked a good chunk of the night to reassure people and answer the stream of calls."

Temblors in western Quebec are rare, but they do cause damage about once every 10 years, according to the USGS. The two biggest damaging earthquakes in the region occurred in 1935 (magnitude 6.1) and in 1732 (magnitude 6.2).

Earthquakes east of the Rockies are often felt over a much broader region, and a few people Ottawa area, 125 miles (200 km) away from Montreal, reportedly felt the overnight shaking.

The damage caused by any single event depends on the quake's depth, proximity to populated areas, building standards in the region, as well as the type of earthquake. The USGS frequently updates the magnitude of an event after more data is analyzed.

An earthquake's magnitude is a measure of the energy released at the source. It is just one predictor of the shaking that may ensue, which is affected by local and regional geology. Scientists know in a general sense what causes Earthquakes but are unable to predict specific quakes.

This article will be updated if significant additional information becomes available. Find more earthquake news here.