Witnesses who alerted emergency services said a pram was involved in the accident, Swedish public broadcaster Sveriges Television reported. Emergency services personnel have since confirmed a pram was involved.
The incident occurred in Ornskoldsvik municipality, close to 600 kilometres north of the Swedish capital Stockholm.
The railway crossing is reported to have boom gates.
Police are working to identify the deceased and are also interviewing witnesses to rule out any foul play.
A crisis team has been called in to support witnesses.
"Shocked witnesses are being brought to a facility and a priest has also been called in to support them," Hakan Wiberg, manager at Ornskoldsvik emergency services, told the television broadcaster.