[R] Is there a package in R that lets me fit a robust linear mixed model?

[Frank Duan]

Dear R people,

Happy Thanksgiving! 

I just wonder if there is a R package that can supply some kind of
"robust" way to fit a linear mixed model. I mean assigning small
weights to those observations with large residuals, like
iteratively-reweighted-least-squares approach.

Many thanks,

Frank