Venus Rajnikant Patel, 45, is missing after catastrophic flooding swept through Nepal's border region with Tibet on Wednesday, Aug. 26.

Patel recently moved back to the West Chester area after years as a software engineer in St. Louis. He was on a religious pilgrimage he had planned for nearly two years, his brother Dennis told WKRC Local 12. He is among approximately 90 Americans still unaccounted for, according to the State Department.

Patel had checked into a hotel in Rasuwagadhi, a border crossing in Nepal's northern Rasuwa district, about 75 miles north of Kathmandu. He sent videos of the valley to his family. His last message said he was in line at the border crossing.

The flooding struck the Bhote Koshi River basin at about 8:40 a.m. local time, ABC News reported. The U.S. Geological Survey determined a glacial collapse and debris flow caused the disaster, not an earthquake as initially reported, according to CBS News.

The death toll had risen past 670 as of Saturday, Aug. 29, with more than 3,000 people still missing, NPR reported. More than half of the missing are foreign nationals. Five Americans have been rescued.

A family reunited, then separated

Dennis Patel said his brother left his career in St. Louis to care for their aging parents and take over the family business. He bought a condo in Liberty Township near the family home. The two made a pact.

"We made a pact as a family, that we should have at least either dinner or lunch together," Dennis told WKRC. "He would go to work, and then he would come and have dinner with us every night."

Patel had traveled to Spain to see a solar eclipse just weeks before departing for Nepal.

Friends search from St. Louis to Kathmandu

Close friend Sandy Gay told WCPO that Patel was the core of their St. Louis friend group. Friends held a prayer vigil Sunday, Aug. 30. One friend flew to Kathmandu to search for Patel in person, WCPO reported.

Gay described Patel as someone who would have been helping others to safety. She said friends are putting out "anything we can into the universe to find him …"

The Patel family has sent recent photos and identifying information to the U.S. Embassy in Kathmandu at the State Department's request, WKRC reported. The Nepal Disaster Search registry lists Patel as still missing, with his last known location at Hotel Kailash in the Timure Bazzar area of Rasuwa district.

The State Department has pledged $500,000 in assistance through Catholic Relief Services for emergency shelter and relief supplies in flood-affected communities. No timeline for concluding search operations has been announced.