Police told news agency TT that the two injured were a man in his 60s and a woman in her 40s.
The blast, at the Varby Gard station in the municipality of Huddinge, which is about 11 kilometers south of Stockholm, took place when someone picked up an object, which then exploded, Swedish Television reported on Sunday.
A man in Stockholm picked up a suspected hand grenade from the ground and it detonated in his hand Sunday, killing him and injuring his companion, Swedish police said.
"It is too early to say", Mr Olsson said.
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However, other media reports have said that a police vehicle ran over the IED, triggering the blast. The injured were shifted to hospital and a search operation is underway, a police officer said.
According to a Swedish police report published a year ago, Sweden is the European country where criminal gangs use the most grenades, often from stocks from the former Yugoslavia. The woman suffered injuries to her face.
Police declined to confirm that report, for which the newspaper named no sources.
Plane disappears after taking off from Oklahoma City
Radar contact of the aircraft was lost about 200 miles northwest of Cancun and showed the aircraft at approximately 15,000 feet. Hypoxia refers to a lack of oxygen, which could happen if the plane was not sealed properly or did not have emergency oxygen.
Police have cordoned off an area outside the entrance to the metro station Varby Gard, and are investigating the incident.
Police in Sweden say a man has been seriously injured after an explosion at a Stockholm subway station.
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Saturday's $570 million jackpot is the fifth-largest Powerball jackpot and the seventh-largest US lottery jackpot. But when the jackpots are as large as they are this week, the store can see between 200 and 300 hopefuls per day.