"According to what is currently known, the windows of the bus were (entirely or partly) smashed and one person was injured," Dortmund police said in a said. The police said the incident happened in Hoechsten, located outside the city.
"It is not yet possible to say exactly what the explosion was or exactly where something exploded," said the statement.
Dortmund said defender and Spanish international Marc Bartra had been taken to hospital.
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The Borussia Dortmund team bus is seen after an explosion near their hotel before the game Reuters
"All of our support to @MarcBartra, @BVB and their fans," Barcelona tweeted in support of their former player.
Police added: "Currently there is no evidence of a threat to the visitors at the stadium."
Borussia Dortmund said in a statement: "Shortly after the departure of the Borussia Dortmund team bus from the hotel to the stadium there was an incident.
"The bus has been damaged in two places. One person has been injured and is in the hospital. At this point we will inform as soon as we know more."
Dortmund later said in a tweet that the match would go ahead on Wednesday at 1645 GMT