Two other explosive devices were found Monday at restaurants in separate parts of the country, The Irrawaddy newspaper in Thailand reported.
Three bombs have exploded since Friday. One bomb killed a man and a woman Friday night at a guesthouse in Taungoo, 137 miles from the capital Yangon. Another woman was hospitalized.
Early Sunday, a bomb went off at a bus stop in northern Yangon, damaging the bus stop and a billboard. No one was injured.
Also on Sunday, two youths were slightly injured when a bomb attacked to the underside of a truck detonated.
Yangon police posted a warning on Facebook Sunday, instructing the public to notify the police or other officials if they find "a strange package."
San Min, a township official in Thaketa where one of the unexploded devices was discovered, said unknown suspects "have intentionally done this." He said an investigation was under way to determine who placed the explosives.