The Kuwaiti newspaper al-Siyasa ("Politics") has published a story claiming Hizbullah is in possession of chemical and biological weapons. This Haaretz report is a pretty accurate translation of the major points of the original article in Arabic.
The article doesn't mention exactly what kinds of weapons Hizbullah has, nor how much of them it has, but it is specific about where the weapons came from (Iran) and where they are now ("Baalbek as well as north and south of the Litani River as of December 2008").
If Hizbullah did have chemical and biological weapons, it would significantly raise tensions between Israel and Hizbullah. But it's not clear that the story is true in the absence of more information.
While physically, Iran would theoretically be able to send chemical or biological weapons to Hizbullah, whether or not it did is a remaining question. The article is based on "European intelligence reports" and is in line with what we would expect Iran's strategy to be to deter Israel from attacking its nuclear program. That being said, the information comes from only one source which is not necessarily a disinterested player, and is not identified in the newspaper article. Al-Siyasa also appears to have a reputation of making bold claims about Hizbullah, including a June 2007 article blaming president Assad himself for a Katyusha attack on Israel.
Additionally, if Hizbullah did have chemical or biological weapons, it's reasonable to assume Israel would have known. Israel runs flights over southern Lebanon pretty frequently, and has something of a human intelligence network in southern Lebanon. If this news were a surprise, the reaction by now from the Israeli government would have been significantly stronger. But if Hizbullah did have chemical and biological weapons and Israel knew, it raises a number of questions:
1) Why would Israel keep it a secret? In 2006 it made no small show of illustrating the links between Hizbullah, Syria, and Iran. It would have altered the PR battle in a way even Israel could have understood was in its advantage. One possible answer is that Israel was aware and was feigning not knowing to improve its intelligence capabilities and to preserve the element of surprise. This is similar to what it did with Syria in 2006 when Israel destroyed an incomplete nuclear facility in that country. There was no previous announcement, which helped Israel's operational security.
2) Why would Hizbullah keep it a secret? One possible answer was that Iran wanted to put the weapons in place, and hold off on announcing them until it was necessary to deter Israel. Also, Syria kept its own nuclear reactor project a secret. So it wouldn't be out of the realm of possibility, and comes with a certain level of precedent.
3) Would Lebanese elections last June have affected an announcement of weapons? Very likely, but it's not clear in which direction. On the one hand, not announcing possession of weapons from Iran would make Hizbullah look more moderate and electible. On the other hand, Hizbullah runs on a campaign of effectiveness, so having WMD would have bolstered that appearance. Nasrallah certainly made a point of bashing Israel as a part of Hizbullah's campaign strategy. But would he have gone to the point of announcing WMD?
In the absence of any definitive answers to these questions, its hard to say that the story definitely is true. That being said, there's nothing to suggest the story is NOT true. In a manner of speaking, knowing that this animal has four legs and hooves, is it a cow? Not necessarily, but nothing suggests it is not. Knowing Iran would be likely to send chemical and biological weapons to Hizbullah if it could, and knowing Hizbullah and Israel might have a reason to keep it a secret, is the story true? Same answer.