The police car and the vehicle it was chasing went off road 591 at Fredrika in Åsele municipality. Both ended up flipped over in Viska lake.
Police press spokesman Peder Jonsson confirmed to the TT newswire that a woman police officer died at the scene while another officer was airlifted to hospital by helicopter.
“We got the call at 3.46am that a police car had gone off the road with two officers and that there was another car in the water with the person being chased,” added emergency control room officer Pelle Bengtsson.
The man in the other car, 25, was unhurt and was brought to the police station in Umeå. He was arrested on suspicion of a range of offences including driving recklessly and driving under the influence of drugs.
The chase began in neighbouring county Västernorrland, where the mood was tense on Thursday morning.
“It's really horrible, of course. We're taking care of our colleagues now,” said Martin Södervall, police control room officer in Västernorrland.
Police later held a minute's silence at 3pm to pay tribute to the dead officer and her colleague, who was seriously injured in the accident but was not reported to be in a life threatening condition.
"What happened is very tragic and we feel grief and despair," said police chief Dan Eliasson in a statement.