MEXICO CITY (AP) -- A Mexican auction house is selling unpublished photos of Mexican muralist Diego Rivera at work.

Galerias Luis C. Morton says the negatives include shots of Rivera painting two of his most famous murals. One shows his wife, Frida Kahlo.

The auction house's Carlos Carballo says the images belong to the assistant of a photographer who knew Rivera during the 1940s and 1950s.

The 37 negatives are being auctioned in two packages on Saturday. One includes 13 images of Rivera working on his murals "Dream of a Sunday Afternoon in Alameda Park" and "Man, Controller of the Universe."

The other includes 24 negatives showing Rivera in his Mexico City studio and in conversation with Siqueiros and Trotsky.