Amazon.com Inc. plans to eliminate gaps in its free same-day delivery service in all 27 cities where it is offered, responding to complaints that some minority neighborhoods are excluded.

Amazon made the pledge in a statement obtained by the Congressional Black Caucus. The organization, which represents black members of Congress, had alerted Amazon it was monitoring the situation and supported calls for an investigation by the Federal Trade Commission into the service boundaries.

Amazon spokesman Craig Berman declined to comment.

Congressman Bobby Rush of Illinois called for an FTC investigation and spoke about the issue on the floor of the House of Representatives. Afterward, Amazon pledged in a letter to Rush to serve Chicago’s South Side in coming weeks.

In addition to Chicago, Amazon made similar pledges to elected officials representing Boston and New York City following complaints that minority communities in those cities were excluded from the service.

Amazon has already expanded the service to Roxbury, which had been excluded.

BLOOMBERG NEWS