Police in Tochigi Prefecture have arrested two Vietnamese men. They are investigating whether the two men were involved in a series of robberies that have taken place over the past month in Tochigi Prefecture, north of Tokyo, and the nearby prefectures of Nagano, Gunma and Fukushima.

One robbery occurred in Tochigi Prefecture's Nikko City on April 30. Two men broke into a house and tied up a 75-year-old resident. They stole over 30,000 yen -- about 200 dollars -- and a cash card before fleeing.

After launching an investigation, police discovered that the stolen cash card had been used at a convenience store ATM in another Tochigi city.

They analyzed security camera footage and identified one of the men as 25-year-old Vietnamese national Hoang Huu Hoa. Police arrested him on Wednesday on suspicion of attempted theft. He reportedly has denied the allegations.

Police also arrested 23-year-old Mai Van Sy, another Vietnamese national who was with Hoang, on suspicion of overstaying his visa.

Prefectural police departments have set up a joint investigation team to look into the two men's alleged involvement in the other robbery cases.

Investigative sources told NHK that a security camera near the robbery site in Gunma captured a car that resembled the one used by the two suspects. The investigation team have seized the car.