SAN LEANDRO -- Witnesses described a horrific scene after a reported explosion near a homeless encampment Tuesday evening, with a pair of badly burned people rushing to a neighboring home for help before being taken to the hospital in critical condition.

Alameda County fire spokeswoman Aisha Knowles said crews were called to the area near the railroad tracks at Hesperian Boulevard and Springlake Drive on reports of an explosion around 9:30 p.m. They discovered two people had been badly injured and summoned a hazardous materials team to the area to look for what caused their injuries, she said.

"There were two adults who ran from the encampment to a nearby apartment to ask for water," Knowles said. "They were in a lot of pain and felt like they were on fire."

They went to the home of Cynthia Silva, who said her boyfriend was telling then to call 911 when a woman suddenly rushed in their front door and ran to their bathtub.

"This lady came in and she had skin hanging off her face and her arms," Silva said. "It looked bad. She was screaming 'Something exploded, something exploded!'"

Cynthia's daughter Brittney, 18, said the woman got in the tub and turned on the water but started screaming even more. A man, who Silva's boyfriend had initially seen, was also badly burned and outside, using the garden hose to wash off.

Knowles said a third person who came into contact with a possible caustic substance from the injured couple was also taken to a hospital.

She said Alameda County sheriff's investigators would take over the investigation.

"What they were not able to find is a link between the incident and the injuries," Knowles said. "That is what they will be investigating."

Contact Eric Kurhi at 408-920-5852. Follow him at Twitter.com/erickurhi.