Chelsea Clinton is back in Puerto Rico stumping for her mother, Democratic presidential candidate Hillary Clinton.

Campaign staffers say about 250 people in the coastal town of Luquillo thronged around the former first daughter on Tuesday as the 28-year-old pushed her mother’s campaign.

Clinton then traveled to her mother’s San Juan campaign headquarters, urging supporters to keep up the pace in advance of the island’s June 1 primary. She also was expected to stump at the island’s biggest shopping mall.

It is the beginning of a three-day swing through the U.S. territory. A total of 55 delegates are at stake in the June 1 vote.

This is Clinton’s second trip to Puerto Rico in the past three weeks.