UPDATED: Rep. Don Young said in a press release that a suspicious white powder sent to his office in Anchorage is concrete.

"The FBI has notified Congressman Young’s State Director, Chad Padgett, that the substance is in fact a mixture of concrete and is not hazardous," the release said.

Other similar packages were sent to the Fairbanks offices of Sen. Mark Begich and Sen. Lisa Murkowski. Begich's spokeswoman Julie Hasquet said that as of 6 p.m. on Monday, Begich had not received a report as to the contents of the package sent to his office.

Murkowski's office was not immediately available.

Both federal buildings were evacuated today.

According to the AP, the box delivered to Begich's office had an Arizona return address.

Here's the press release from Rep. Don Young's office:

Today a package was sent to Alaska Congressman Don Young's Anchorage office that when opened, it was discovered to contain a white substance. After cooperating with the authorities, the Anchorage office was cleared of the package and the white powder. The FBI has notified Congressman Young’s State Director, Chad Padgett, that the substance is in fact a mixture of concrete and is not hazardous.  It is not clear at this time why the package with the concrete mixture was sent to Congressman Young. 

Again, the FBI, Federal Protection Service, Anchorage Police Department and Anchorage Fire Department are to be commended for their excellent work today and for responding so quickly. Congressman Young's Anchorage office will be open tomorrow and the staff will be back at work.