Volunteers are facing expensive shipping costs and long delivery times due to limited access to the island.
More than a week after Hurricane Maria hit Puerto Rico
, millions of people in the US territory are still in the dark and food is becoming scarce.
Non-perishable items and other donations sit at Puerto Rico's main port of San Juan
and have yet to be delivered -- or are held up at ports in the US mainland. And only a handful of flights are traveling to the island.
Students at a New York high school are filling up their school's auditorium with water, boxes of cereal and canned foods but can't find a way to send them to the island.
Sending donations to Puerto Rico could cost the Comsewogue High School in Long Island between $17,000 and $25,000, school officials told CNN affiliate WABC reported
"I have probably called over 25 to 30 companies. All through Long Island, a couple of companies down in Florida," Vince Roman, a physical education teacher, told WABC.
In New Orleans, a group of pilots and aviation enthusiasts, who collected about 25,000 pounds of supplies and flew them to Texas after Hurricane Harvey, are shifting their focus to Puerto Rico.
"Puerto Rico, USVI, and other areas affected have no idea how many people are behind them and ready to assist! We're anxious to get down there!," the Cajun Airlift group posted on Facebook.
Volunteers at Casa Puertorriqueña, a group that organizes the annual Puerto Rican Parade in Chicago's Humboldt Park neighborhood, have filled up at least eight trucks with everything from flashlights and batteries to canned goods and baby diapers, CNN affiliate WGN-TV reported.
But the donated goods remain in a warehouse.
"We can't get these companies to fly this stuff to Puerto Rico," said Vilma Colom, community outreach and engagement volunteer at Casa Puertorriqueña told WGN-TV. "We're not getting the help that we need like everybody else has gotten during these crises."
Members of the Puerto Rican community in Los Angeles are also mobilizing to send help.
They turned a Cuban supper club in Hollywood into a donation center and slowly have been sending supplies.
"We have our hands tied in a lot of ways but we are not stopping," said Ana Miró, a member of Los Angeles for Puerto Rico.
The group already sent some donations on Delta and JetBlue relief flights and plan to send more aid in the coming weeks.
"We plan to gather things and keep sending them," Miró said. "We are not stopping for any reason."