A report today in the official New Light of Myanmar said the return address on the package was for an embassy in Burma, but did not say which one.
The newspaper called the explosion a "timely attempt" to disrupt stability in the country and blamed the blast on what it called "internal and external destructive elements."
The report did not say what it meant by "timely attempt," but the blast comes just days after the United States failed in its bid at the United Nations Security Council to pass a resolution on Burma.
The proposed resolution called on Burma's military leaders to speed up their progress toward democracy and stop attacks on ethnic minorities.
China and Russia cast a double veto against the resolution last week.
In the past, Burma's military-run government has blamed small bomb attacks on exile groups that oppose military rule.
Some dissidents say the blasts are carried out by government-linked groups to justify tighter security.
Burma has been under military rule since 1962.
Information for this report is provided by AP and AFP.