Wallström said three Swedes were wounded in the attacks and three have not yet gotten in touch with the authorities or their family. Earlier on Wednesday, four Swedes were unaccounted for but one was eventually found unharmed.
"Family members are very concerned and we can not rule out anything. We hope that our contacts with Belgian authorities mean we'll get some answers about where they are or, at best, that they contact us," Wallström told Swedish Radio News.
On Tuesday, Belgian officials asked people in Brussels to limit the use of their telephones after the network became saturated with traffic.
Foreign Ministry spokeswoman Karin Nylund told Radio Sweden on Wednesday morning that Swedes in Belgium should keep an eye on local media reports as well as the embassy's website, which is being updated continuously with new information and advice.
The minister said Sweden is working with its consulate in Brussels as well as the appropriate Belgian authorities. Sweden has also offered Belgium assistance and support following the terrorist actions though has not received any formal request for help.
Of the three Swedes injured in the blasts, two were men with minor wounds and the other was a pregnant woman who was hospitalized with serious injuries, according to news agency TT.
Wallström told Swedish Radio News that the terrorist attacks filled her with great dismay and anger. She previously worked at the European Commission and was based in the Belgian capital.
"This is a place that my family and I called home for more than 10 years," she said.