SAO PAULO (AP) — Brazilian authorities are investigating arsons at two separate residences where Venezuelans were living that they believe were committed by the same person, a police official said Friday.

On Monday, a person threw an incendiary device into a house in the northern city of Boa Vista, injuring a man and a woman, police investigator Cristiano Camapum told reporters at a press conference. On Thursday, a similar attack occurred at another house, and two adults and their 3-year-old child were injured. Several Venezuelans were living in each house.

Grainy security camera footage of Monday's incident shows a man setting something alight and then throwing it over a wall around the house.

Camapum said authorities believe they have identified a suspect and that he committed both acts and possibly a third similar attack on a business last month. But investigators are still trying to determine if the presence of foreigners in the houses was a motive for the attack.

Thousands of Venezuelans who are fleeing hunger and unrest in their homeland have poured into the neighboring Brazilian state of Roraima in recent years. The state is struggling to cope with the influx of people, many of whom are living on the streets. Just in Boa Vista, state officials estimate there are now 40,000 Venezuelans — in a city with a population of about 330,000.

Roraima has asked the federal government for help, and officials promised Thursday to send more federal security forces to help patrol the border.