Eleven previously reported packages contained what looked to be homemade explosives with black powder.

EVERETT — The FBI is investigating more potential bombs they believe could have been mailed by an Everett man with a history of mental problems.

Thanh Cong Phan, 43, previously was believed to have sent 11 packages that showed up last week at government offices in and around the nation’s capital. Among other destinations, they were mailed to the White House, CIA, FBI headquarters and military installations in Virginia and Washington, D.C.

The FBI and United States Postal Inspection Service now believe that number is closer to 18.

“The FBI has recovered additional packages that appear similar to those allegedly mailed by Mr. Phan …,” said FBI spokeswoman Ayn Dietrich-Williams. “Further assessment is needed before a definitive connection can be established.”

As with the previously reported packages, the newest batch were sent to agencies in and around Washington D.C., she said.

“All packages were sent to government facilities,” Dietrich-Williams said. “We don’t have specific information indicating additional packages still in the mail system, but out of an abundance of caution, (investigators) continue to be poised to detect and safely recover any additional packages.”

Previously reported packages contained what appeared to be a homemade explosive using a glass bottle filled with black powder, fixed with a fuse and a GPS, court papers say.

The U.S. Attorney’s Office in Seattle on Thursday released a copy of a court-approved search warrant and a list of what agents have seized from Phan’s home.

The inventory includes jars and bottles with powder and fuses, U.S. Postal Service priority mail labels, commercial fireworks, wire, electrical tape, cellphones and SIM cards, Superglue, cinnamon, sugar and chili powder.

The defendant was linked to the mailings after U.S. Postal Service inspectors used a tracking number on one sent to FBI headquarters. That package was mailed March 16 from a USPS kiosk in Mill Creek. Surveillance photos reportedly show Phan sending the item, according to court papers.

Phan made at least six calls to Snohomish County 911 this year, at all times of the day and night. One of those calls was placed from the Mill Creek post office.

In one call, Phan told 911 that terrorists were using invisible cameras to monitor his communications and control his body. At times, he mentioned Naval Station Everett.

He said he had tried to report the torture to local police and the FBI for years.

Each of the first 11 packages Phan is suspected of sending contained a typed letter “with ramblings about neuropsychology, mind control, and other subjects, including terrorism,” according to court papers.

Phan was known to federal agents for having sent similar messages before, according to court papers.

Phan now is charged in U.S. District Court in Seattle with one count of shipment of explosive materials. If convicted of the felony, he could be sentenced to up to 10 years behind bars, officials said.

Eric Stevick: 425-339-3446; stevick@heraldnet.com.