Warren Buffett's 18 percent stake in Burlington Northern Santa Fe is worth even more today (Tuesday), after the railroad reported a 30 percent increase in first quarter earnings, beating Wall Street's expectations.  (BNSF's Q1 conference call has been posted on the company's web site.)

The stock is once again traded at an all-time high today, approaching $106 a share before retreating.  Current price:

Burlington Northern's profits are getting help from the commodities boom.  While the railroad's fuel costs are higher, it's doing big business moving in-demand agricultural products and coal.  Revenues from moving ag products increased a whopping 38 percent to $866 million.

As we noted about two weeks ago in the WBW post Warren Buffett's Railroad Ride Paying Off as Burlington Northern Hits All-Time High,  Burlington shares have been rallying strongly since Buffett's Berkshire Hathaway completed its most recent round of Burlington buys in January.  At midday today, they're up almost 35 percent from the close on January 22.  That was the last day of a string of purchases in the mid to high $70s.

As you can see from the links at the bottom of this post, Buffett also accumulated Burlington shares last summer and fall.

Later today on CNBC's Fast Money at 5p and 8p ET, Dylan Ratigan and the traders will discuss how Buffett has been "going to work" while almost everyone on Wall Street is mired in the credit crunch.

UPDATE:  That Fast Money discussion is now history.  Lee Brodie has a nice summary on the Fast Money Rapid Recap blog.

Current Berkshire price:

See Warren Buffett Watch on CNBC's The Call, most weekday mornings at 11:50a ET

Questions?  Comments?  Email me at buffettwatch@cnbc.com