Reading row (+, -) column with file fread, data.table

I am trying to use fread to read the genome alignment in data.tablein R. Here is a snapshot of the alignment file:

USI-EAS28:1:100:1786:674#0/1    +   1_maternal  68326824      CTCAATTATACTGAAAGAAACACAATATATCATA    IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
USI-EAS28:1:100:1786:940#0/1    +   16_maternal 11407541    CTATTAGTGACCTGCTGTGGGACCTTGGGATGGT  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
USI-EAS28:1:100:1786:705#0/1    +   1_maternal  63849584    CTGAGGGTTTGTGTCAGGAAGGGGTGTGGAATTG  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   0:T>C
USI-EAS28:1:100:1786:1168#0/1   -   5_maternal  31381649    GCATCATTCATGAAACAATTTTCAAGAGAGGAAA  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
 USI-EAS28:1:100:1787:582#0/1   +   10_maternal 54587781    CTACAATAATAATAGGGGACTAAAACACCCCACT  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
 USI-EAS28:1:100:1787:62#0/1    +   10_maternal 70390747     CTATTTGCTACTGAATTGTTAATTTTAAAACAGT IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
 USI-EAS28:1:100:1788:573#0/1   -   7_maternal  92583837     CACTGTCAACATTAGACAGACCAATGAGACAAAG IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
 USI-EAS28:1:100:1788:854#0/1   +   7_maternal  129611206    GTTTGTTTTTTTTTTTGAGATGGAGTCTCATTTT IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   32:C>T
 USI-EAS28:1:100:1788:185#0/1   -   13_maternal 23694307    CAAACAAACTCAAAATGGACTATCGACTGAAAAA  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   
 USI-EAS28:1:100:1788:1339#0/1  -   13_maternal 33699510    TTAACTCTAGTTTTTAGGGATTGCAAATTAGACG  IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII  0   0:A>G

The second column reports that the line that it is reading is aligned ( +- forward, -- reverse). Unfortunately, fread tries to read this column as an integer, always assigning a value of 0. This column should be read as a character or even logical, for that matter. Trying to play with arguments sepand sep2does not help.